CD Laboratories Test Catalog

CD Laboratories provides testing for joint infection as part of a comprehensive test panel. For more information on comprehensive panels and/or individual tests, please contact us.

Synovasure Comprehensive Infection Panel

The Synovasure Comprehensive Infection Panel consists of a combination of proprietary and standard of care (SoC) synovial fluid tests to aid in the diagnosis of Periprosthetic Joint Infection (PJI) and Ntive Septic Arthritis (NSA) using a single aspiration of fluid.

The Synovasure Alpha Defensin for PJI ELISA test is a laboratory developed test (LDT) consisting of assays for synovial fluid alpha defensin and C-reactive protein (CRP). It has been validated for use as an adjunct to aid in the diagnosis of PJI using the 2013 Musculoskeletal Infection Society (MSIS) criteria for diagnosing PJI. Final result is provided as a qualitative result: Positive, Negative or Indeterminate.

The Synovasure Alpha Defensin for NSA ELISA is a laboratory developed test (LDT) consisting of assays for synovial fluid alpha defensin and lactate. Final result is provided as a qualitative result: Positive, Negative or Indeterminate.

Note: Synovasure Alpha Defensin for NSA has not been validated for the diagnosis of NSA, due to lack of industry standard criteria.

The Synovasure Microbial Identification LDT is a bead-based assay intended for the early detection of microbial antigen in synovial fluid. The current test panel identifies Staphylococcus species, Enterococcus species, Candida species and Cutibacterium acnes (formerly P. acnes).

The assay can detect microbial antigen in some specimens where an organism is present but was not cultured.

The Synovasure Neutrophil Elastase (NE) LDT was designed to be a proxy for white blood cell (WBC) count and may be used in place of the Leukocyte Esterase (LE) test strip, which can serve as one of the criteria in the MSIS infection algorithm. The NE LDT is designed and validated specifically for synovial fluid, while the LE test strip is designed for urine. The NE LDT is not prone to the high rate of invalid results due to blood contamination that have been reported with the LE test strip. A positive NE result should be interpreted as meeting the MSIS criteria of a positive LE test strip.

Anaerobic and aerobic culture bottles incubated for 7 days. Includes organism identification and antibiotic susceptibilities. Shoulder specimen cultures are supplemented to enhance growth and incubated for 14 days.

Automated high-performance cell count system with differential and RBC count. Elevated white blood cells (>3000 cells/mm3) are confirmed with a manual count.

An assessment of synovial fluid using polarized light microscopy is performed for the presence of CPPD (calcium pyrophosphate dihydrate) and/or MSU (monosodium urate) crystals.

The accuracy of diagnostic tests such as synovial fluid white blood cell count, neutrophil percentage, and others, can be significantly impacted by the quality of the specimen that is submitted for evaluation. As part of every analysis, specimen integrity tests are performed. Physicians are notified when a suboptimal specimen has been submitted. Specimen integrity tests assess:

  • Absorbance at 280nm (A280) – Specimens that fall outside the normal range for synovial fluid may be caused by dilution via saline lavage or use of contrast agents
  • Red Blood Cell Count – Specimens are verified as characteristic of synovial fluid, not blood.

Synovasure Differential Diagnosis Arthritis Panel

Synovasure Osteoarthritis (OA) testing includes tests for cartilage oligomeric matrix protein (COMP) and interleukin-8 (IL-8). The COMP ELISA and IL-8 ELISA are quantitative laboratory-developed tests (LDTs) intended to detect COMP and IL-8, respectively, in the synovial fluid of patients experiencing knee joint pain with suspected arthritis. Results are used in combination to provide clarification in diagnosing osteoarthritis.

  • COMP (-) (below 1500 ng/mL) suggests little to no evidence of cartilage damage
  • COMP (+) (above 1500 ng/mL) suggests cartilage damage
  • COMP/IL-8 ratio (+) (above 4.3 ng/pg) suggests isolated, idiopathic OA
  • COMP/IL-8 ratio (-) (below 4.3 ng/pg) suggests cartilage damage and elevated inflammatory status

The values for COMP and IL-8 are assigned using purified recombinant proteins and internal analytical procedures and are not metrologically traceable to an international reference standard.

Synovasure Rheumatoid Arthritis (RA) testing includes tests for anti-cyclic citrullinated peptide (anti-CCP) and rheumatoid factor (RF). The qualitative Anti-CCP ELISA and quantitative, immunoturbidimetric RF Latex are LDTs intended to detect Anti-CCP and RF, respectively, in the synovial fluid of patients experiencing joint pain or inflammation with suspected arthritis. Results are used in combination to provide further clarification in diagnosing rheumatoid arthritis.

Negative results on the Anti-CCP ELISA and RF Latex should not be used to aid in the exclusion of RA from the differential diagnosis.

Synovasure Crystalline Arthritis testing includes an assessment of synovial fluid using polarized light microscopy is performed for the presence of CPPD (calcium pyrophosphate dihydrate) and/or MSU (monosodium urate) crystals.

Automated high-performance cell count system with differential and RBC count. Elevated white blood cells (>3000 cells/mm3) are confirmed with a manual count.

If the final cell count is >3,000 cells/mmand/or PMN% >70%, specimens are reflexed to Synovasure Alpha Defensin for NSA test to determine if elevated levels are due to infection or another cause.

Synovasure Alpha Defensin for NSA ELISA test consists of assays for synovial fluid alpha defensin and lactate. Final result is provided as a qualitative result: Positive, Negative or Indeterminate.

  • Alpha Defensin (-) suggests no evidence of NSA, regardless of lactate result
  • Alpha Defensin (+), lactate (-) or below 70.0 mg/dL is indeterminate for NSA
  • Alpha Defensin (+), lactate (+) suggests NSA

Note: Synovasure Alpha Defensin for NSA has not been validated for the diagnosis of NSA due to lack of industry standard criteria for benchmarking.

The accuracy of diagnostic tests such as synovial fluid white blood cell count, neutrophil percentage, and others, can be significantly impacted by the quality of the specimen that is submitted for evaluation. As part of every analysis, specimen integrity tests are performed. Physicians are notified when a suboptimal specimen has been submitted. Specimen integrity tests assess:

  • Absorbance at 280nm (A280) – Specimens that fall outside the normal range for synovial fluid may be caused by dilution via saline lavage or use of contrast agents
  • Red Blood Cell Count – Specimens are verified as characteristic of synovial fluid, not blood.